"Reactive diluents" are understood to be low-viscosity liquids which dilute resin-like binders and thus provide the coating composition with the viscosity required for its application, contain functional groups capable of reaction with the binder and, during the hardening process, become part of the hardened coating to a predominant extent, depending on their volatility.
Numerous compounds have been proposed as reactive diluents both for crosslinker-containing and for air-drying coating compositions based on polyesters or alkyd resins; see for example, S. Enomoto et al., J. Appl. Polym. Sci. 22, 253-265 (1978); S. Hochberg, J. Oil Colour Chemists' Assoc. 48, 1043-1068 (1965); D. B. Larson/W. D. Emmons, "The Chemistry of High Solids Alkyd/Reactive Diluent Coatings", Coatings Conference, Athens 1982; DE-OS Nos. 24 46 760, 31 15 071 and 31 51 366. However, most of the proposed compounds have been unable to live up to expectations because they lead either to reduced gloss in the case of pigmenting and to a marked reduction in gloss on weathering or to extended drying times and, in some cases, even to tacky surfaces.
In addition, the compounds hitherto recommended as reactive diluents, due to their structure, are suitable in principle only for air-drying coating compositions or only for crosslinker-containing coating compositions. By contrast, there is no known class of reactive diluents for both binder systems.
The object of the present invention is to provide reactive diluents which overcome the disadvantages of the prior art so that it is possible to obtain lacquer systems based on alkyd resins and/or oil-free polyesters containing reactive diluents which harden in the requisite times to form satisfactory coatings and which contain no organic solvents or only small quantities of organic solvents which do not act as reactive diluents.